Differences in how cotton varieties grow, and why it’s important? An XtendFlex® update
Home » Differences in how cotton varieties grow, and why it’s important? An XtendFlex® update
Print

Differences in how cotton varieties grow, and why it’s important? An XtendFlex® update

Larissa Holland, Michael Bange and the CSD Extension Team 

At a glance

  • This study aimed to analyse the developmental and growth patterns of CSD’s varieties containing Bollgard® 3 XtendFlex® traits and determine if they differ significantly from previous Bollgard 3 varieties. 
  • Analyses shows that day degrees are a primary driver of most crop development characteristics and accounted for the most variability in different rates of measured variables, including heigh and node development, and boll accumulation. 
  • Variety and region did not significantly impact key developmental characteristics suggesting that the growth patterns are largely consistent across different varieties and growing regions once day degrees are accounted for.  
  • Changes in the rate of nodes above white flower (NAWF) decline is more influenced by crop management practices than day degrees. 
  • The growth patterns of varieties containing XtendFlex are largely consistent with those of previous Bollgard 3 varieties. This conclusion is based on an analysis of data from over 65 crops grown over three seasons.  

Comprehensive and regular monitoring of cotton crops’ development is important for achieving optimal crop performance. As new varieties come to market, there is a need to understand how they might develop differently so that management can be adjusted accordingly.  This detailed analysis of varieties also helps to underpin the optimal crop development curves that are used in CottonTracka®, one of CSD’s online agronomic tools. 

How did we analyse the data? 

Detailed measurements of crop development of varieties containing XtendFlex® was undertaken by the CSD extension team over three seasons (2021 to 20024) across 65 crops in all cotton growing regions.  Measurements included frequent measurements of crop height, node development, boll numbers, and changes in nodes above white flower (NAWF).  In addition, the timing of the first flower flowering, NAWF count at first flower, and the length of the flowering period to cutout were also measured. This was the same approach that was taken for a previous analysis for varieties that contained the Bollgard® 3 and Round Up Ready Flex® traits. Varieties used in this study were Sicot 619B3XF, Sicot 761B3XF, Siokra 253B3XF and Sicot 743B3XF.  

As anticipated, there was substantial variation in the data collected from growing crops in different fields across Australia. The statistical analyses aimed to determine whether this variation in measured variables over time could be explained by  

  • day degrees (15/32),  
  • the region in which the crop was grown and finally  
  • whether variety has an influence.  

The analyses were conducted at a 95% statistical confidence level, indicating that any identified differences are likely to be genuine and not due to random chance. The results on the analyses were then compared to the outcomes previously generated for Bollgard 3 Round Up Ready Flex varieties.  

What we found 

For most factors, most variability is accounted for using day degrees, except for decline in NAWF which saw crop management (which were differences associated with the field where crops were individually managed) being the most significant contributor. Region and variety were not significant factors on any of the key development characteristics.  

Figure 1: The level of variability accounted by day degrees, specific, crop management, region and variety in the statistical analysis of measured crop variables for varieties containing Xtendflex. The chart highlights the dominant role of day degrees in explaining variability and note that at np time did region or variety help explain the variation measured across crops.

Figure 1: The level of variability accounted by day degrees, specific, crop management, region and variety in the statistical analysis of measured crop variables for varieties containing Xtendflex. The chart highlights the dominant role of day degrees in explaining variability and note that at np time did region or variety help explain the variation measured across crops. 

It was important to note that post flowering analysis for both height and nodes had the highest undetermined variability, which may represent variations or outliers within the dataset or could be related to specific management practices. It is most likely however, that the variation was a result of these responses having fewer data points in comparison to pre flowering periods.  Similar outcomes were determined for Bollgard 3 varieties (see Australian Cottongrower Vol 44).  

To understand how the overall responses of the varieties containing XtendFlex compared to the previous varieties containing Bollgard 3 Roundup Ready Flex traits, we plotted the data for the different variables against day degrees, fitted a linear regression to that data and compared this regression developed in the original analysis (Figures 2 to 4). All graphs show that the developmental responses for the varieties containing XtendFlex are like previous varieties (that is the orange regression line is very similar to the blue regression line in all graphs) 

Figure 2: Boll accumulation (left) and NAWF decline (right) height versus day degrees. The orange line is the linear regression through the data presented for varieties containing XtendFlex, while the ‘blue’ line represents the regression generated for data from the previous analysis for varieties containing Bollgard 3 and roundup ready flex traits, The r2 value represents the outcome for fitting the regression to the recent XtendFlex data (the orange line).

Figure 2: Boll accumulation (left) and NAWF decline (right) height versus day degrees.  The orange line is the linear regression through the data presented for varieties containing XtendFlex, while the ‘blue’ line represents the regression generated for data from the previous analysis for varieties containing Bollgard 3 and roundup ready flex traits, The r2 value represents the outcome for fitting the regression to the recent XtendFlex data (the orange line).  

Figure 3: Node development height versus day degrees. The graph on the left shows the data and response prior to flowering while the graph on the right is the response post flowering. The orange line is the linear regression through the data presented for varieties containing XtendFlex, while the ‘blue’ line represents the regression generated for data from the previous analysis for varieties containing Bollgard 3 and Roundup Ready Flex traits. The r2 value represents the outcome for fitting the regression to the recent XtendFlex data (the orange line).

Figure 3: Node development height versus day degrees.  The graph on the left shows the data and response prior to flowering while the graph on the right is the response post flowering.  The orange line is the linear regression through the data presented for varieties containing XtendFlex, while the ‘blue’ line represents the regression generated for data from the previous analysis for varieties containing Bollgard 3 and Roundup Ready Flex traits. The r2 value represents the outcome for fitting the regression to the recent XtendFlex data (the orange line). 

Figure 4: Plant Height Comparison. The graph on the left shows the data and response prior to flowering while the graph on the right is the response post flowering. The scatter plot compares plant height between XtendFlex (blue data points) and Bollgard 3 Round Up Ready Flex (orange line) cotton varieties when accumulated day degrees exceed 600. The blue dotted line represents the line of best fit for the XtendFlex data, accompanied by the corresponding equation and R-squared value.

Figure 4: Plant Height Comparison. The graph on the left shows the data and response prior to flowering while the graph on the right is the response post flowering.  The scatter plot compares plant height between XtendFlex (blue data points) and Bollgard 3 Round Up Ready Flex (orange line) cotton varieties when accumulated day degrees exceed 600. The blue dotted line represents the line of best fit for the XtendFlex data, accompanied by the corresponding equation and R-squared value. 

Summary and Looking Forward 

Over 65 crops that utilised varieties containing XtendFlex from three years were analysed and compared to the results from previously assess varieties containing Bollgard 3 Round Up Ready Flex traits. The slopes of the trend lines for height, nodes, NAWF and boll accumulation were consistent between the two sets of cotton varieties. While there were some variations in the slopes for boll accumulation and plant height at lower day degrees, these differences were likely due to a smaller data set or natural variations. The consistent trend lines between the two varieties indicate that there is no need to generate new equations or ‘cotton curves’ for CottonTracka. 

This research provides valuable insights for cotton growers and consultants. By understanding that different cotton varieties exhibit similar growth patterns dependant of day degrees, they can effectively utilise CottonTracka to monitor crop development and make informed management decisions. The continued monitoring of new varieties will ensure that CottonTracka remains a valuable tool for the cotton industry.